Patrice Fromy

Mitigation of electromagnetic instabilities in fast ignition scenario

We address the issues of collective stopping for intense relativistic electron beams ~REB! used to selectively ignite precompressed deuterium1 tritium ~DT! fuels. We investigate the subtle interplay of electron collisions in target as well as in beam plasmas with quasi-linear electromagnetic growth rates. Intrabeam scattering is found effective in taming those instabilities, in particular for high transverse temperatures.

Thomas–Fermi‐like and average atom models for dense and hot matter

All the Thomas–Fermi approaches to the thermodynamics and atomic physics properties of dense and ionized matter consisting of a single element are systematically derived and compared within a density‐functional theoretical framework. The corresponding results are contrasted to those of the average atom model by using similar approximations for exchange, correlation, and gradient corrections. Emphasis is led on equations of state, ionization, level shifts, and radial moments. The same numerical algorithms are used to unravel similar trends or identify specific ones, in terms of density and temperature variations. The most sophisticated Thomas–Fermi–Dirac–Weizacker method yields the closest results to the hybrid average atom model using quantized bound states. Parameters ranges of potential interest for inertially confined thermonuclear fusion stress out density in the 0.1–10 times the solid, and temperature up to 10 keV.

Transportation of nitrogen atoms in an atmospheric pressure post-discharge of pure nitrogen

In this paper, the transportation of nitrogen atoms in a flowing post-discharge of molecular nitrogen at atmospheric pressure is studied. The axial variation of the density of nitrogen atoms is modelled and compared with measurements. A relatively high initial density, i.e. several 1014 atoms/cm3, is obtained by this approach, showing also that the main losses are caused by volume and surface recombination during transportation. A low value is found for the recombination probability of the used polyamide surface (around some 10−4) allowing therefore quite long transportation times and distances.

Correlated stopping of relativistic electrons in superdense plasmas

The electromagnetic stopping of intense and relativistic electron beams (REB) arising from femtosecond lasers interacting with a precompressed deuterium+tritium (DT) fuel is investigated within the Bohr–Fermi formalism with a large impact parameter. Dynamical intrabeam correlations through long-range collision with target electrons are shown to be quantitatively significant for various arrangements of projectile electrons and the overall REB penetration in the DT fuel. One thus expects much shorter stopping ranges yielding an easier access to fuel ignition through hot spots production.

Heavy-Ion/Hot Target Interactions of Inertial Confinement Fusion Interest

A few basic atomic problems are associated with the stopping of nonrelativistic pointlike ions in dense and hot matter. First, the free electron contribution is considered, taken in random phase approximation with an exact dynamic dielectric function, valid at any temperature. Stopping power and straggling can thus be obtained for any projectile velocity. The temperature dependence is of special relevance for a projectile energy <5 MeV/amu. The mean excitation energies of bound electrons are then considered and found to be smaller than in cold matter. The projectile effective charge in hot targets is also investigated. Experiments involving a heavy-ion beam produced by a standard accelerator and interacting with an independently produced coronal plasma are described.

Low velocity ion stopping in binary ionic mixtures

Attention is focused on the low ion velocity stopping mechanisms in multicomponent and dense target plasmas built of quasiclassical electron fluids neutralizing binary ionic mixtures, such as, deuterium-tritium of current fusion interest, proton-heliumlike iron in the solar interior or proton-helium ions considered in planetology, as well as other mixtures of fiducial concern in the heavy ion beam production of warm dense matter at Bragg peak conditions. The target plasma is taken in a multicomponent dielectric formulation a la Fried–Conte. The occurrence of projectile ion velocities (so-called critical) for which target electron slowing down equals that of given target ion components is also considered. The corresponding multiquadrature computations, albeit rather heavy, can be monitored analytical through a very compact code operating a PC cluster. Slowing down results are systematically scanned with respect to target temperature and electron density, as well as ion composition.

Correlated stopping of relativistic electrons in supercompressed DT fuel

The electromagnetic stopping of intense and relativistic electron beams (REB) arising from femtosecond lasers interacting with a precompressed deuterium-tritium (DT) fuel is investigated within the Bohr-Fermi formalism with a large impact parameter. Dynamical intrabeam correlations in the target are shown to be quantitatively significant for various arrangements of projectile electrons and the overall REB penetration in the DT fuel.

Atomic physics for inertial fusion using average correlated hydrogenic atom model

The influence of discrepancies between analytical expressions for charge changing cross section on the ionization state of swift heavy ions interacting with hot and dense plasmas is analyzed within the framework of our new average correlated hydrogenic atom model. Making use of our Classical Trajectory Monte-Carlo results, we show that the partial charge transfer cross section into the projectile atomic levels has the same importance as the total charge transfer cross section.

Low-velocity ion slowing-down in strongly asymmetric and binary ionic mixtures

Attention is focused on the low-ion-velocity stopping mechanisms in multicomponent and dense target plasmas built of quasi-classical electron fluids neutralizing binary ionic mixtures. The target plasma is taken in a multicomponent dielectric formulation a la Fried-Conte. The occurrence of projectile ion velocities (so-called critical) for which target electron slowing-down equals that of given target ion components is also considered. We emphasize the strongly asymmetric BIM targets such as the proton-boron 11 of thermonuclear concern and the strongly mass-asymmetric proton-U238+.

Correlated Stopping of Relativistic Electron Beams in Supercompressed DT Fuel

Fundamental features of dynamically 2-correlated relativistic electrons in the MeV energy range and interacting with very dense and hot hydrogenic plasmas of fusion interest are thoroughly investigated. The target is modelled with a Drudelike dielectric function. Longitudinal and undramped pair correlations along overall drift velocity are contrasted to transverse ones decaying exponentially over several tens of target screening length λD. Other novel behaviours include a much higher response to target temperature variations, than to density ones, for the ratio of 2-correlated to uncorrelated stopping.